Various interactive haptic technologies exist, which provide a user or users with tactile information or feedback, often in combination with visual information displayed on an interactive screen. For example, previous haptic feedback devices include pins moving to physically change a deformable surface. A pen connected to an articulated arm may be provided, as in the SensAble PHANTOM device. Alternatively, a user may wear, for example in the form of a glove, one or more actuators which are activated to provide haptic feedback to a user. However, in each of these technologies, a user requires physical contact with a deformable surface, a pen, or a specially adapted glove. Such requirements reduce the usability and spontaneity which with a user may interact with a system.
Tactile sensations on human skin can be created by using a phased array of ultrasound transducers to exert an acoustic radiation force on a target in mid-air. Ultrasound waves are transmitted by the transducers, with the phase emitted by each transducer adjusted such that the waves arrive concurrently at the target point in order to maximise the acoustic radiation force exerted.
However, existing ultrasound haptic devices do not allow for the provision of distinctive multiple localised feedback points in mid-air. A user is not able to distinguish between such multiple localised feedback points if they are separated only by a small distance. Therefore, there is also a limit to the resolution of the haptic feedback devices which in turn limits how useful such devices can be.
Examples of when a high resolution haptic feedback device could be useful include when a user cannot properly see a display because they are driving, or when a user does not wish to touch a display because they have dirty hands. It would be advantageous to be able to provide user feedback above such a surface in order to allow information to be transmitted via an additional, haptic, channel in parallel with or as an alternative to the visual display.
The subject matter described herein seeks to mitigate the above-mentioned problems.